Fuel injection apparatus for internal combustion engines

ABSTRACT

A fuel injection apparatus in which metering of the fuel is determined by adjustable stops controlling the stroke of a shuttle piston, one of the stops being positionally adjustable by an eccentric frusto-conical cam mounted for translational movement along its axis in response to an absolute pressure sensing evacuated bellows and for rotation about said axis by a temperature sensing expansible capsule with both the bellows and the capsule mounted in an air inlet duct through which air flows to the manifold of the engine served by the apparatus under the control of a manually adjustable throttle valve.

United States Patent [:91

Pagdin 1 1 FUEL INJECTION APPARATUS FOR INTERNAL COMBUSTION ENGINES [75] lnventor: Brian Colin Pagdin, Sutton Coldfield, England [73] Assignee: GKN Transmissions Limited,

Birmingham, England [22] Filed: Mar. 5, 1973 [21] Appl. No.: 338,681

[30] Foreign Application Priority Data Mar. 4, 1972 United Kingdom 9944/72 [52] U.S. C1 123/140 MC; 123/140 CC; 123/124 A; 123/119 D; 123/140 MP; 123/179 L [51] Int. C1. F02D 1/04; F02D 1/06; FOZM 39/00 [58] Field oiSearch "123/140 MP, 140 CC, 123/139 AM, 119 D, 140 MC, 124 A, 179 L [56] References Cited UNITED STATES PATENTS 2,062,260 11/1936 Weber 123/124 A 2,852,011 9/1958 Pringham.. 123/140 MC 2,907,313 10/1959 Hebert 123/140 MP FUEL TANK 1 Dec. 23, 1975 3,020,905 2/1962 Goschel 123/179 L 3,030,027 4/1962 Reppert U 123/124 A 3.680.536 8/1972 Clark 123/140 MC 3.689.036 9/1972 Kikuchi 123/127 FOREIGN PATENTS OR APPLICATIONS 920,799 4/1947 France 123/140 CC Primary Examiner-Wendell E. Burns Assistant ExaminerRonald B. Cox Attorney, Agent, or Firm-Spencer & Kaye [57] ABSTRACT A fuel injection apparatus in which metering of the fuel is determined by adjustable stops controlling the stroke of a shuttle piston, one of the stops being positionally adjustable by an eccentric frusto-conical cam mounted for translational movement along its axis in response to an absolute pressure sensing evacuated bellows and for rotation about said axis by a temperature sensing expansible capsule with both the bellows and the capsule mounted in an air inlet duct through which air flows to the manifold of the engine served by the apparatus under the control of a manually adjustable throttle valve.

13 Claims, 6 Drawing Figures INLET MMIFOLD U.S. Pat e nt Dec. 23, 1975 Sheet 1 of 5 51.0w- OFF VALVE SHAFT 1 2 METERING UNIT INPUT L INJECTOR b CARBURATOR \JJONTROL MEANS FUEL) FUEL) PUMP FILTER FUEL TANK \|6\INLET MANIFOLD U.S. Patent Dec. 23, 1975 Sheet 2 of5 3,927,653

U.'S. Patent Dec. 23, 1975 Sheet 3 015 3,927,653

Sheet 4 of 5 3,927,653

US. Patent Dec. 23, 1975 US. Patent Dec. 23, 1975 SheetSofS 3,927,653

FUEL INJECTION APPARATUS FOR INTERNAL COMBUSTION ENGINES BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to fuel injection apparatus for an internal combustion engine comprising means defining an air inlet duct, an adjustable throttle valve means controlling flow of air therethrough to the engine, fuel inlet means and fuel outlet means for connection to one or more injectors, pump means for establishing flow of fuel from said inlet means to said outlet means at an injecting pressure for delivery from said injectors, metering means for delivering a measured quantity of fuel to said outlet means in each cycle of operation of the engine, and drive means for driving said metering means in timed relation with said engine.

The invention has been developed in relation to fuel injection apparatus of the kind specified intended for use in conjunction with an engine having one or more cylinders and having ignition means for igniting the air-fuel mixture in the cylinders by means of spark discharge. The fuel is a volatile hydro-carbon such as petrol.

Also, the invention has been developed primarily in relation to a fuel injection apparatus of the kind specitied wherein the metering means comprises a metering cylinder containing the free or shuttle piston element movable between stops, the distance between which is determined by an adjustment means to determine the quantity of fuel delivered each stroke of the free piston and cylinder spaces on opposite sides of the piston are connected in successive cycles of operation through commutating valve means respectively to the pump means and to the outlet means, the other valve space in each case being connected respecively to the outlet means and the pump means. If the fuel injection apparatus is intended to be utilised in conjunction with a multi-cylinder engine the outlet means would comprise a plurality of outlets and the commutating valve means would be associated with, or would be constructed to act as, a distributing valve means to effect delivery of fuel from respective outlets in the proper succession.

A current environmental problem is avoidance or minimisation of pollution of the atmosphere by exhaust gases from internal combustion engines. For this purpose there is an increasingly stringent requirement accurately to control the quantity of fuel delivered to the engine in each cycle of operation to ensure complete combustion thereof, and to this end it is especially important to avoid operation at air-to-fuel ratios which are too rich, i.e. contain a greater quantity of fuel than can be completely burnt.

When attempting to operate an engine at a constant and proper air-to-fuel ratio to achieve this non-polluting condition (which ratio is appreciably weaker than those habitually obtaining with engines equipped with carburettors) a typical air-to-fuel ratio which it is desired to maintain being between and 17:1, it is important to avoid any further weakening of the mixture otherwise the engine will misfire and there will be loss of power and also excessive pollution of the atmosphere due to the expulsion of unburnt mixture. The ratio of air-to-fuel referred to above is a ratio of weight of air and fuel.

A further requirement which it is desirable to meet to achieve satisfactory performance of an engine is to provide momentary enrichment of the mixture (a lower air-to-fuel ratio) to meet a sudden demand for increased power as, for example, when a road vehicle equipped with an engine having a fuel injection apparatus of the kind specified is accelerated by sudden opening of the throttle valve, as distinct from gradual opening of the throttle valve.

2. Description of the Prior Art There are two possible ways of establishing that the required ratio is achieved.

The first is known as the mass-flow system (as applied in carburettors) which attempts to measure the weight of the air aspired by the engine in a given time and deliver in the same time that weight of fuel which will give the required ratio. Considerable difficulty is encountered in trying to measure actual weight of air aspired by the engine. The main problem is to achieve a signal of sufficient magnitude without interferring with the breathing of the engine, since such signal is derived by providing a venturi section or the equivalent in the air inlet duct through the carburettor.

Also in internal combustion engines in which the air and fuel mixture is supplied through a carburettor, a sudden opening of a throttle valve, as by sudden depression of the accelerator pedal where the engine IS installed in a vehicle, tends to produce a hesitation before acceleration of the engine occurs.

The cause of this hesitation is that there is a relatively long column of air-fuel mixture between the carburettor and the inlet valves of the engine, typically of the order of 12 inches to 20 inches, and until this column can be accelerated, the engine does not receive the additional fuel and air which it requires to accelerate.

To avoid or reduce this undesirable effect it is common practice to provide carburettors with an accelerator piston operating in a chamber containing liquid fuel and serving, when the piston is displaced suddenly, to feed an increment of fuel into the air inlet duct. This piston is ordinarily operated by link means connected to the throttle linkage so that the additional delivery of fuel takes place before the throttle valve is opened, and the demands of the engine are thus anticipated by enriching the column of air-fuel mixture before it reaches the inlet valves of the engine. This expedient is effective to reduce the hesitation which occurs. On the other hand, once acceleration of the column has taken place, the air-to-fuel ratio incorporated therein is then markedly over-rich and can lead to quite severe atmospheric pollution in traffic conditions in which a large number of vehicles are being repeatedly stopped and accelerated.

The second way of establishing the required air-tofuel ratio is known as the speed-density system (as employed in fuel injection apparatus of the kind specitied). This involves use of engine speed to control both the air aspired and the fuel delivered (the volume of air aspired per minute depends on the rpm. of the engine and the quantity of fuel delivered per minute is also made dependent upon the rpm. by driving the fuel metering means in timed relation with the engine). It is then necessary to measure the parameter of air density, which can be done by measuring its pressure and its temperature and use this as an additional control over the fuel delivered. This system provides more accurate control than the massflow system, but fuel injection apparatus previously proposed has generally involved sensing the difference between pressure in the air inlet duct and external atmospheric pressure. This entails the complexity of having to provide a further pressure sensing means for sensing atmospheric pressure so that the air-to-fuel ratio may be maintained at a correct value at different altitudes.

The main object of the present invention provides a new or improved fuel injection apparatus of the kind specified incorporating a speed-density control means in which the parameters of air pressure and temperature are sensed accurately and in a simple, and hence reliable and economic manner.

A further object is to provide an improved means for short term enrichment of the air-fuel mixture to meet the demand for sudden acceleration and yet which will not produce such a high degree of atmospheric pollution as that entailed in conventional means as incorporated in carburettors.

SUMMARY OF THE INVENTION temperature responsive sensing means for sensing air temperature in said air inlet duct, each of said pressure and temperature sensing means providing a mechanical output, mechanism operatively connected between said pressure sensing means and said temperature sensing means on the one hand and said metering means on the other hand for imparting to the latter a a setting which is a function of both absolute pressure and air temperature in said air inlet duct.

A further preferred feature of the invention is that the temperature sensing means comprises an expansible chamber providing a mechanical output in a mode which is relatively unaffected by environmental mechanical disturbance arising from air flow through said air inlet duct. Further, the pressure sensing means may also comprise an expansible chamber supported together with the temperature sensing chamber, said mechanism providing for appropriately combining the mechanical outputs of the two chambers.

Thus, one form of pressure sensing means preferably comprises an evacuated enclosure which has internal spring means tending to expand it anad external spring means opposing the expansion, which latter occurs in response to decrease in the absolute pressure in said air inlet duct.

As hereinafter more fully explained, the advantage of this arrangement is that it facilitates the establishment of a high accuracy as to the ratio between the output (displacement) provided by the evacuated enclosure and the value of absolute pressure in the air inlet duct.

The sensing of absolute pressure renders the computation of air-to-fuel ratio valid irrespective of external atmospheric pressure and consequently a vehicle equipped with an engine having this apparatus can operate satisfactorily at different altitudes.

A further feature is that there may be provided in the fuel injection apparatus valve means responsive to an engine temperature parameter for admitting a con trolled quantity of air to the air inlet duct otherwise than by way of the manually controlled throttle valve serving to regulate the admission of air to said duct. The effect of this is to enable speed of engine operation to be increased when the engine is operating under cold conditions, e.g. when started after a period of idleness, and thereby reduces the risk of the engine stalling when idling.

According to a further aspect of fuel injection apparatus of the kind specified incorporates the improvement wherein said sensing means comprises a main pressure sensing means for sensing pressure in said air inlet duct, a temperature sensing means for sensing air temperature, supplementary pressure sensing means for sensing a sudden change of the pressure of air in said inlet duct in response to sudden opening of said throttle valve means, mechanical means for transmitting mechanical output from all of said sensing means respectively to said metering means for setting the latter in accordance with a combination of the respective parameters sensed by said main and supplementary sensing means and said temperature sensing means.

The approach represented by the present invention is in fact quite different, although the preferred form does make use of an accelerator piston as hereinafter mentioned. In the present invention the additional increment of fuel is fed in by the same injectors as normally serve to inject fuel to the inlet manifold of the engine, but the timing of the delivery of this additional increment of fuel is determined by the increase in absolute pressure in the air inlet duct which results from, rather than precedes, opening of the throttle valve. The column of air-fuel mixture which is thus enriched is much shorter than is the case for a carburettor equipped engine, because the fuel injectors are mounted on the inlet manifold adjacent to the respective inlet valves of the engine, and consequently the phenomenon of overenrichment which occurs in the carburettor equipped engine by virtue of the long air fuel column is entirely avoided.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described, by way of example, with reference to a specific embodiment thereof illustrated in the accompanying drawings wherein:

FIG. 1 is a schematic diagram illustrating the main components of the fuel supply system incorporating a fuel injection apparatus in accordance with the invention;

FIG. 2 is a view in side elevation and partly in crosssection illustrating a constructional embodiment of the fuel injection apparatus in accordance with the invention;

FIG. 2A is a fragmentary view in cross-section on the line AA of FIG. 2;

FIG. 3 is a plan view in cross-section on the line 3-3 of FIG. 2 illustrating the carburettor device incorporated in the fuel injection apparatus;

FIG. 4 is a cross-sectional view on the line 44 of FIG. 2 of the body of the apparatus;

FIG. 5 is a diagrammatic view illustrating the general arrangement and manner of operation of the metering means comprising the metering piston and cylinder unit and assembly and a commutating and distributing valve means of the fuel injection apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENT The complete system for supply of fuel, such as petrol, to an internal combustion engine is shown in FIG. I. The system comprises a fuel tank 10 connected by a pipe 11 to the inlet of a low pressure fuel pump 13 through the intermediary of a fuel filter l2 and thence by a pipe 14 to the inlet 14a of the fuel injection apparatus indicated generally at 15.

The fuel injection apparatus 15 is mounted directly on the inlet manifold 16 of an internal combustion engine 17 of the kind in which ignition of the fuel is effected by sparking plugs. By way of example the engine is illustrated as having six cylinders in V formation.

The fuel injection apparatus comprises the following main units or sub-assemblies, namely a high pressure pump 18 having its inlet connected to the pipe 14, a metering means which includes a commutating and distributing valve means 19, and a metering unit 20 in the form of a cylinder and free or shuttle piston movable between stops. The high pressure pump 18 and the commutating and distributing valve means 19 are driven at half crankshaft speed by an input shaft 21 through the intermediary of a belt 22 which is toothed internally for engagement with externally toothed pulleys on the shaft 21 and on the crankshaft extension or other driven shaft 23 of the engine.

Fuel at high pressure from the outlet of the pump 18 is fed through commutating ports of the commutating and distributing valve means 19 to the metering unit 20 and then back to the distributing ports of the valve means 19 passing thereafter to injectors 26 through respective pipes 27 connected to outlets of the body of the apparatus fed via the valve means 19, so that the injectors receive pulses of fuel in the required sequence. The injectors are mounted in openings in the inlet manifold 16 of the engine.

The fuel injection apparatus further comprises a sensing or control means 29 for controlling operation of the metering unit 20 to determine the ratio of air-tofuel supplies to the engine in accordance with parameters sensed by the control means 29. The fuel injection apparatus has an air flow duct through which air can flow to the inlet manifold 16 under the control of a manually operated valve such as a butterfly valve. The term manually is of course to be deemed to include foot operation.

The fuel injection apparatus also includes a carburettor device 30 to enable the engine to be started without the latter having to be driven to a high cranking speed as previously explained. Further, a blow-off valve 31 is provided connected to the outlet of the high pressure pump 18 for returning fuel through a pipe 32 to the tank 10. Fuel in excess of the requirements of the fuel injection apparatus, typically about twice the amount required to meet maximum demand, is withdrawn by the high pressure pump 18 and circulated back to the tank via the blow-off valve 31 and pipe 32, and provides for cooling of the high pressure pump and associated parts.

Referring now to the constructional embodiment shown in FIG. 2, the body 33 of the fuel injection apparatus comprises an upper part 330 affording an elongated chamber in which is accommodated the high pressure pump 18, the commutating and distributing valve means 19, and the metering unit or assembly 20. The lower part 33b of the body which may be formed integrally with the upper part is generally rectangular box-shape in form and affords a chamber 34 which communicates with the passageway 35 extending through a sleeve-like throttle valve fitting 36 containing a manually controlled butterfly valve plate 37 fixed on a rotatable spindle 38. The chamber 34 is open at three sides, namely the front and rear sides as seen in FIG. 2 and also the lower side. The fitting 36 can be attached to any of these sides, one of the remaining sides being closed by a plate and the other connected over the inlet aperture afforded by the inlet manifold 16 of the en gine. This arrangement permits of some variation in the manner of mounting the fuel injection apparatus on any given engine so as best to suit the throttle linkage thereof and must make the best use of the space in the engine compartment for the accommodation of anciliary parts such as an air filter.

The chamber 34 which thus forms part of an air inlet duct extending from the air inlet 39 of the fitting 36 to the open side of the chamber 34 applied over the inlet aperture of the inlet manifold so as to accommodate the main components of the sensing or control means 29 for sensing the parameters of absolute pressure of inlet air in the chamber 34 and the temperature thereof to control operation of the metering unit 20. The crosssectional area presented to air flow by the chamber 34 around the sensing means 29 is in fact at least as great, and preferably greater, than that presented by the throttle section 36 when the valve plate 37 is fully open. Thus the controlling signal, i.e. pressure sensed by 29, is derived without imposing air constriction on engine breathing." Also because of its position the sensing means 29 responds instantaneously to pressure changes without the delay which could be entailed were it mounted in a remote chamber connected by pipe to the chamber 34.

The body parts 330 and 33b may be formed as castings of a light alloy such as an aluminium alloy.

The high pressure pump 18 is of the rotary vane type and comprises a rotor 40 mounted between stator plates 41 and 42 spaced apart by a ring 41a and having radial vanes 43 of carbon. The rotor is fixed on the drive shaft 21 which is rotatably mounted in a ball bearing 44a at one end and in a plain journal bearing 44b in the stator plate 42. Fuel such as petrol is admitted through an inlet 14a to a chamber 18a at the intake side of the high pressure pump 18 and which may be equipped with a filter 18b as shown.

Delivery of fuel from the high pressure pump takes place to a space 46 through one or more openings in the stator plate 42.

Before referring to the construction of the metering means it is convenient to refer to FIG. 5 which illustrates diagrammatically to general arrangement and manner of operation thereof, such metering means including the metering unit 20 and the commutating and distributing valve means 19.

The commutating and distributing valve means comprises a rotary asembly which includes a rotary carrier 47 fixed to the driving shaft 21 and affording a shallow cylindrical recess for receiving a rotary valve plate 48, to which is attached a large diameter rotary valve plate 49. The plate 48 has a flat 48a at one side engaging a flat in the carrier 47 to ensure positive drive from the latter to the plates 48, 49 which are cemented or otherwise secured together face-to-face.

The rotary valve plate 49 is maintained in pressure contact with the opposed face of the metering cylinder block 50 in which the metering cylinder 51 extends transversely to the axis of rotation of the rotary valve plates.

The cylinder 51 contains a free or shuttle piston 52 which is movable between stops 54 and 55. The metering cylinder block has outlets g1 to 6 for connection to 7 respective pipes 27 leading to the injectors 26, these outlets being connected by way of passageways extending axially through the block with portsfl tof6 respec tively traversed in succession by a port d in the rotary valve plate 49 thereby acting as a distributing means.

The function of ports e1, e2 in the block 50, and which are connected by passageways Sla, Slb to the cylinder spaces S1, S2 above and below the piston 52 respectively is to operate in combination with ports cl to c6 in plate 49 and with ports b1, b3, b5 in plate 48 together with a T-shaped surface passageway formed in the left-hand face but not extending through the thickness of the plate 48, and having branches b2, b4, b6, as a commutating means to produce one stroke of the piston 52 from its upper limit to its lower limit or vice versa for each traversing of a port ft to 16 by the port d, and thereby deliver a measured quantity of fuel (dependent upon the length of the stroke of the piston 52) to the outlet g] to g6 concerned.

The full line arrows S6 illustrate the flow of fuel to the upper cylinder space .51 of cylinder 51 during the stroke of the piston 52 which is effective to expel fuel as shown by the broken line arrows 57 from the lower cylinder space s2 and deliver it from the outlet g6.

It will be evident that fuel from the high pressure pump traverses the ports a], bl, cl, e1 to reach cylinder space 31. Fuel from the cylinder space s2 traverses the ports 22, c4, limb b4, limb b6, port djfi, g6. When the driving shaft has rotated through a further 60 (corresponding to an engine crankshaft rotation of 120), fuel from the high pressure pump will traverse ports a5, b5, 05 (then in the lowermost position), e2 to reach cylinder space 32. Fuel in cylinder space s1 will be delivered through ports e1, c2, limb b2 (then in the topmost position), limb b6, port d, and g5. This position is shown in H6. 2. Similarly, after the next 60 of rotation, another fluid flow path will be established causing movement of the piston 52 in the opposite direction and delivering a measured quantity of fuel from the next outlet g4 and so on.

A spring 58 reacting between the inner or bottom face of the recess in the carrier plate 47 and the smaller diameter rotary plate 48 urges the plates 48, 49 into contact with the ported face of the metering cylinder block 50. At least the plate 49 is made of a material which provides good sealing properties with respect to the face of the cylinder block 50 and of a material which will have a suitably long service life. In practice both plates may be made of carbon, whereas the block 50 may be made of steel,

In order to control the stroke of the free piston 52, the sensing means 29 senses certain selected parameters, namely absolute pressure of air in the inlet duct downstream of the throttle valve 37, namely in the chamber 34, and also temperature of this air. The absolute pressure is preferably sensed by a single device in the form of an evacuated enclosure, preferably, as shown, a bellows 60 which comprises an axially contractable and expansible corrugated side wall 61 and end plates 62 and 63 which are urged apart by a preloading means such as coiled compression spring 64. It will be noted that the bellows being mounted in the air inlet duct itself will be subjected to the absolute pressure of the air therein which is about to enter the inlet manifold (as distinct from being in a chamber which is connected by a relatively small diameter pipe to the air inlet duct).

The end plate 62 of the bellows is fixed to a cam element 65 of generally frusto-conical form with its frusto-conical face 66 eccentric to the axis 67 about which the cam element and the bellows can rotate. For this purpose the cam element is mounted on a hollow spindle 69, the internal bore of which is open to atmosphere at an air inlet 70. The spindle and cam element have respective axially extending slots 69a, 650 forming an air inlet valve means. These slots are in circumferential register or overlap when the engine is cold and thus provide for admission of a controlled quantity of air for fast idling. When the engine temperature rises the cam 65 rotates as hereinafter described to move the slots out of circumferential overlap and close the valve.

The other end plate 63 of the bellows is mounted rotatably through a substantially sealed bearing 71 in the interior of an accelerator piston 72 movable axially in a cylindrical chamber 73 afforded by the lower part 33b of the body.

The end plate 63 is itself mounted on a sleeve 74 which forms the output element of an adding mechanism indicated generally at 75 and which serves to add two further parameters which are sensed, namely the temperature of the air in the chamber 34 sensed by an element 76 and another selected temperature sensed by the element 77, such as a temperature parameter related to engine temperature.

As hereinafter described, the outputs of these two sensing elements 76 and 77 are transmitted to the sleeve 74 as a rotation, and since end plate 63 of the bellows is fixed, in a rotational sense, to the sleeve 74, the bellows and cam element 65 are rotated to adjust the position of the lower stop 54 through the intermediary of a tappet 78 carrying a roller 79.

The end plate 62 and the cam element are also displaced axially in response to pressure variations in the chamber 34. Accordingly the position of the lower stop 54 is determined by all the sensed parameters in combination.

The bellows tends to be expanded by the internal spring 64 reacting against virtue spring 80 disposed in the spindle 69. It is required to maintain high accuracy as to the value of the This, of axial travel of the cam element 65 to absolute pressure in the chamber 34. Since the wall 61 of the bellows has some resilience and the spring 64 cannot readily be changed or adjusted once it has been inserted into the bellows due to evacuation of the interior, selection of the effective spring rate produced by the combination of the springs 64 and 80 is achieved by selecting the latter.

The temperature sensing elements 76 and 77 may be of the wax capsule type such as are commonly employed in engine cooling systems for controlling the flow of fluid, each comprising an axially expansible chamber containing a substance, for example a wax, selected to undergo a vapour pressure change at a predetermined temperature or over a narrow range of temperatures, thereby producing a marked axial expansion of the capsule.

The capsule 76 has a mounting portion supported in the interior of the sleeve 74 whilst the capsule 77 has a mounting portion supported in the interior of a housing 82, the opposed end faces of the capsule constituting the outout portions bearing against the opposite ends of the addition mechanism 75.

The addition mechanism serves to add the outputs of the elements 76 and 77 algebraically and comprises two axially interfitting sleeves 83 and 84, each of which has two diametrically opposed slots extending over a quarter of the circumference of the sleeve leaving .a pair of axially projecting part-cylindrical arms, such as 83a, 840 with the arms of one sleeve fitting axially and slidably in the slots of the other sleeve, so that the two sleeves are capable of relative axial movement but are in driving relation with each other rotationally.

The sleeve 83 which is displaceable axially by the sensing element 76 has a helical slot 85 in which engages a radial pin 86 projecting radially inwardly of, and fixed to, the output sleeve 74.

The sleeve 84 also has a helical slot 87 which is engaged by a radially inwardly projecting pin 88 fixed to the housing 82.

The two sleeves 83 and 84 are urged apart by a coiled compression spring 89 so that each is kept in contact with the output portion of its respective temperature sensing element 76 and 77 as the case may be.

Axial movement of either sleeve 83, 84 produced by expansion of its associated temperature sensing element thus produces an increment of rotation of this sleeve and these increments are additive in producing rotation of the output sleeve 74. Such rotation is transmitted as a displacement of stop 54 as already referred to.

The housing 82 is adjustable angularly about axis 700 by slackening a clamp ring 82a. Such adjustment is transmitted via pin 88 and the adding mechanism 75 to cam 65. The housing 82 is rotatable relative to chamber 91 but sealed with respect to it by sealing rings 91a.

The temperature parameter applied to sensing element 77 may be the temperature of the cooling fluid of the engine, in which case this may conveniently be circulated through a cavity 90 in chamber 91. Alternatively, the outer chamber 91, which in part defines this annular cavity, may be omitted and the housing 82 may be finned externally to partake of the temperature of the compartment in which the engine is installed. The present invention is concerned with the provision of a simple and hence reliable low cost means for effecting momentary enrichment of the mixture entering each engine inlet valve when the throttle is opened suddenly, but without incurring the quite severe pollution effects which result in enrichment of a long column of air-fuel mixture such as exists in carburettor equipped engines.

Whereas in carburettor equipped engines the means for effecting enrichment is usually bperated by connection to the throttle valve linkage and arranged to come into operation slightly before the throttle valve is fully open (to counteract the long delay before the enriched part of the air-fuel mixture will reach the engine inlet valve concerned), the arrangement adopted in the present apparatus responds to pressure in the chamber 34 and thus comprises a supplementary pressure sensing means for applying a positional adjustment to the stop 54 through the same mechanism as the bellows 60.

The supplementary pressure sensing means comprises an accelerator piston 72. This is urged towards that end of accelerator cylinder 73 which communicates directly with air inlet duct 34, i.e. the left-hand end. The right-hand end communicates with duct 34 through a leakage path providing some constriction and hence delay as hereinafter mentioned. The piston is urged to the left by the coiled compression spring 89 acting through sleeve 83, sensing element 76 and sleeve 74 on which the sealed bearing 71 is fixed axially between end plate 63 and a shoulder on the sleeve 74.

a If a sudden increase of absolute pressure takes place in the chamber 34 as a result of sudden opening of the throttle valve, the piston 72, which at its right-hand side will be subjected to the former absolute pressure, is moved to the right producing axial movement of the cam element 65 and lowering of the stop 54 produced momentary enrichment of the mixture.

The piston 72 will gradually move back to its former position under influence of the spring 89 at a rate determined by leakage of air past the piston and some leakage through the bearing 71 which is not quite impermable. This rate can be selected to ensure that very little atmospheric pollution will occur.

Such movement of the accelerator piston does not produce rotation of the sleeve 74 since the sleeve 74, sensing element 76 and sleeve 83 will all move in unison.

It is to be noted that the temperature sensing element 76 is, by virtur of its enclosure in sleeve 74, subject to some delay in its response to air temperature changes in chamber 34. This however, is not critical (as would be delay in responding to pressure changes) because air temperature changes occur as long term variations, whereas air pressure changes are rapid and short term dictated by the degree of opening of the plate 37 and changes in engine speed.

The temperature sensing means is constructed and mounted to provide a stable mechanical output notwithstanding its environmental conditions, e.g. the mode of the mechanical output, namely axial movement of an end wall of the sensing element or capsule 76, is not disturbed by engine vibration and air current traversing chamber 34.

The pressure of fuel delivered from the high pressure pump 18 may be of the order of 120 lbs. per square inch but this is not devel ped at cranking speeds which are capable of being attined by operation of a normal starter motor on the associated engine.

Accordingly the fuel injection apparatus includes a carburettor device 30 which comes into operation only during starting operations at cranking speeds.

It is necessary to prevent duplicate delivery of fuel by way of both the carburettor device and the injectors of the fuel injection apparatus, and accordingly a controlling signal is applied to the carburettor to disable this in a manner such as to prevent delivery of fuel from the carburettor device when conditions of operation in the fuel injection apparatus are such that delivery of fuel from the outlets thereof to the injectors is established. One convenient signal which may be employed for this purpose is a fluid pressure signal derived from the out put side of the high pressure pump.

The carburettor device is illustrated more particularly in FIG. 3 and FIG. 4 and comprises a carburettor bore formed in the body 33 of the fuel injection apparatus along an axis parallel to that of the driving shaft and the bellows and situated about midway between these components in that wall of the body 33 which forms the boundary between the chamber 34 on the one hand and the chamber in which the metering cylinder block, commutating and distributing valve means, and high pressure pump on the other hand are accommodated.

The carburettor bore 100 includes portions 101 and 102 respectively of larger and smaller diameters. Slidably mounted in the smaller diameter portion 102 is one element 103 of ajet assembly. Such element comprises an inner tube 104 having a fuel passageway I05 1 1 extending axially through it and terminating in an end portion 106 of enlarged diameter containing a threshold valve which includes a valve seat element 107, a ball 108 and a biasing coiled compression spring 109 urging the ball into the seat element.

The seat element 107 has an opening 110 in its end face through which liquid fuel in the annular space 111 can pass, the annular space 111 in turn being fed with fuel through passageway 136 connected internally-with inlet 14a on the body of the apparatus.

The strength of the spring 109 is selected to provide opening of the threshold valve at a predetermined low pressure which is greater than any gravitational pressure of fuel at the valve but less than fuel injection pressure, for example about 2 lbs. per square inch. This can be developed by the low pressure fuel pump 13. The valve is thus effective to prevent draining of fuel through the carburettor device gravitationally when the engine and fuel injection apparatus is at rest.

The valve element 103 also includes a head 113 which is a close fit in the smaller diameter portion 102 of the carburettor bore and is equipped with a sealing ring 114 seated in a groove to seal the annular space 111 from the remaining portion of the carburettor bore.

The jet assembly includes a further jet element 115 in the form of an outer tube fitting telescopically with the inner tube 104 and formed with holes 116 constituting a jet orifice extending through its wall at diametrically opposed positions adjacent to the free or delivery end of the inner tube 104.

The carburettor device further comprises two valves, namely a fuel cut-off valve and an air cut-off valve.

The valves comprise a plunger 117 incorporating or operable by a piston portion 117a and movable axially in the larger diameter section 101 of the carburettor bore between an open position, as seen in FIG. 3, and a closed position in which its inner end overlaps the mouth or opening of an air passageway 101b traversing the larger diameter portion 101 of the carburettor bore situated in the vicinity of the free or delivery end of the inner tube 104. Air is admitted to this passageway by pipe 101a (FIG. 4) which may be connected to an air cleaner (not shown), the passageway continuing by way of a portion 101b (FIG. 4) connecting the carburettbr bore and the chamber 34.

The fuel shut-off valve further comprises a valve element 118 of resilient material seated the bottom of a bore 119 in the plunger 117, which bore constitutes a continuation of the interior surface of the outer tube 115 of the jet assembly.

The plunger 117 is biased by means of a coiled compression spring 120 acting between the head 113 and the plunger 117 to maintain the latter in a position in which both the fuel cut-off and air cur-off valves are open.

Movement of the plunger 11! to close both of these valves takes place in response to the admission of fuel under pressure from the-outlet of the high pressure pump 18 to the space 121 through bores 123, 122 and it see 131 whicch communicates with the outlet side of t e high pressure pump through bore 1310 (FIG. 4) formed in an inlet plug fitting 124 screwing into an internally threaded end portion of the carburettor bore, such fitting being equipped with a sealing ring 125 seated in a circumferential recess therein.

The bore 123 may contain a restrictor bush 126 formed with a constrictor passageway 127 to control the rate of admission of fuel under pressure to the space 121 and hence to determine the duration of the starting period for which the carburettor device remains operative, such period terminating with closure of the fuel and air cut-off valves under injecting pressure of fuel in the space 121.

When the throttle valve of the fuel injection device is closed, or only slightly open, pressure in the air inlet duct downstream of this valve is low and air will be drawn through the air inlet pipe 101a of the carburettor device because the cross-sectional areas of pipe 101a and passageway 1016 are small compared with the main air inlet duct of the throttle valve fitting 35 and chamber 34. The air velocity will be higher than that which would be produced by opening the throttle valve plate 36. Fuel delivered from the free or delivery end of the inner tube 104 and emerging from the holes 116 in the outer tube will thus readily be broken up into particles in the manner of a slow running jet assembly of the conventional carburettor, and will be conveyed along the passageway l01b connecting the carburettor device to the chamber 34 of air inlet duct of the fuel injection apparatus.

The carburettor device is also able to supply fuel to the engine in the event of a fault developing in the high pressure fuel pump such as to prevent the pressure at the outlet thereof reaching a value at which it will effect delivery of fuel from the outlets of the fuel pump to the injectors, and such that the plunger 117 remains in the position shown in FIG. 3. For operation under these conditions the throttle valve 36 would be opened only to a slight extent.

Pressure control and relief of fuel delivered from the outlet of the high pressure fuel pump is regulated by a blow-off valve 31. This comprises a valve head 128 (FIG. 3) of conical form cooperating with a valve seat in a body 129 against which is spring loaded by a coiled compression spring 13 High pressure fuel is fed through a bore 1310 to a chamber 131 from which it passes through a filter 133 to the interior bore 134 of the body 129 of the blow-off valve. The latter opens at a pressure determined by the spring to discharge excess fuel to the portion 135 of the blow-off valve bore and thence to a passageway 136. The passageway 136 communicates with the annular space 111 from which excess fuel is fed back to the fuel tank via an outlet fitting 112.

1 claim:

1. in fuel injection apparatus for an internal combustion engine said apparatus comprising means defining an air inlet duct, an adjustable ,throttle valve means controlling flow of air therethrough to the engine, fuel inlet means and fuel outlet means for connection to one or more injectors, pump means for establishing flow of fuel from said inlet means to said outlet means at an injecting pressure for delivery from said injector, metering means for delivering a measured quantity of fuel to said outlet means in each cycle of operation of the engine, and drive means for driving said metering means in timed relation with said engine, the improvement comprising the provision in combination of:

a. sensing means for controlling operation of the metering means and including i. a single pressure sensing means for sensing absolute pressure of air in said air inlet duct,

ii. a temperature responsive sensing means for sensing air temperature in said air inlet duct, each of said pressure and temperature sensing 13 means providing a mechanical output,

b. mechanism for receiving said mechanical outputs from said pressure sensing means and said temperature sensing means on the one hand and transmitting a mechanical output to said metering means on the other hand for imparting to the latter a setting which is a function of both absolute pressure and air temperature, representing air density, in said air inlet duct,

c. enclosure means having boundary walls defining a chamber in direct communication with the air flow path through said inlet duct, said chamber being common to and enclosing said pressure sensing means and said mechanism, for isolating said pressure sensing means and said mechanism from the influence of any pressure medium other than the air in said inlet duct, said apparatus being free of any mechanical inputs to said mechanism which traverse said boundary walls,

. means directly mechanically connectiing said pressure sensing means and said mechanism within said chamber for transmitting said mechanical output from said pressure sensing means to said mechanism without traversing any of said boundary walls of said chamber.

2. The improvement according to claim 1 wherein said pressure sensing means comprises;

a. an evacuated bellows,

b. means separate from said bellows for providing a reference force against which said bellows operates.

3. The improvement according to claim I wherein a. said pressure sensing means and temperature sensing means include respective means for converting pressure and temperature changes into mechanical energy providing movement of respective output elements,

b. said metering means includes an input element movable to vary the quantity of fuel delivered to said outlet means in each cycle of operation of the engine,

c. said mechanism is connected to transmit the mechanical energy required by such metering means to said input element from said output elements with said pressure sensing means and temperature sensing means themselves forming the energy sources for adjusting the setting of said metering means.

4. in fuel injection apparatus for an internal combustion engine said apparatus comprising means defining an air inlet duct, an adjustable throttle valve means controlling flow of air therethrough to the engine, fuel inlet means and fuel outlet means for connection to one or more injectors, pump means for establishing flow of fuel from said inlet means to said outlet means at an injection pressure for delivery from said injectors, metering means for delivering a measured quantity of fuel to said outlet means in each cycle of operation of the engine, and drive means for driving said metering means in timed relation with said engine, the improvement comprising the provision in combination of:

a. sensing means for controlling operation of the metering means and including i. a single pressure sensing means for sensing absolute pressure of air in said air inlet duct,

ii. a temperature responsive sensing means for sensing air temperature in said air inlet duct,

each of said pressure and temperature sensing met... providing a mechanical output,

b. mechanism for receiving said mechanical outputs from said pressure sensing means and said temperature sensing means on the one hand and transmitting a mechanical output to said metering means on the other hand for imparting to the latter a setting which is a function of both absolute pressure and air temperature, representative of air density, in said air inlet duct,

c. enclosure means having boundary walls defining a chamber common to and enclosing said pressure sensing means and said mechanism for isolating said pressure sensing means and said mechanism from external and atmospheric pressure, and

d. means connecting said pressure sensing means and said mechanism within said chamber for transmit ting said mechanical output from said pressure sensing means to said mechanism without traversing any of said boundary walls of said chamber,

e. said mechanism including an output member mounted for displacement relatively to said enclosure means along an axis in response to operation of said pressure sensing means and mounted for rotation about said axis in response to operation 0 said temperature sensing means, and

f. said output member having one of its ends operatively connected to or engaged by said pressure sensing means, and the other of its ends enclosed by said enclosure means to avoid presentation of an end face of said output member to atmospheric pressure externally of said enclosure means.

5. The improvement according to claim 4 wherein said output member comprises a cam having a circumferential face presenting a variable throw in the direction of the circumference and presenting a variable radius at different positions along said axis.

6. ln fuel injection apparatus for an internal combustion engine comprising a body having an air inlet duct, an adjustable throttle valve means controlling flow of air therethrough to the engine, fuel inlet means and fuel outlet meand for connection to one or more injectors, pump means for establishing flow of fuel from said inlet means to said outlet means at an injecting pressure for delivery from said injectors, metering means for delivering a measured quantity of fuel to said outlet means in each cycle of operation of the engine, and drive means for driving said metering means in timed relation with said engine, the improvement comprising the provision in combination of:

a. valve means responsive to an engine temperature parameter and arranged for admitting a controlled quantity of air to said air inlet duct otherwise than by way of said throttle valve means,

b. sensing means for controlling operation of the metering means and including i. a single pressure sensing means substantially isolated in the body of the apparatus from external atmospheric pressure, for sensing absolute pressure of air in said air inlet duct,

ii. a temperature responsive sensing means for sensing air temperature in said air inlet duct, each of said pressure and temperature sensing means providing a mechanical output, and

c. mechanism operatively connected between said pressure sensing means and said temperature sensing means on the one hand and said metering means on the other hand for imparting to the latter a setting which is a function of both absolute pressure and air temperature in said air inlet duct, said mechanism including an output member mounted for displacement along an axis by operation of said pressure sensing means and for rotation about such axis by operation of said temperature sensing means, and said valve means being operatively associated with said output member for movement between an open position and a closed position in response to rise of temperature sensed by said temperature sensing means.

7. The improvement according to claim 6 wherein:

. said output member is rotationally supported on a hollow spindle,

said hollow spindle has a bore which communicates with the external atmosphere,

c. said spindle and said output member have ports which register or overlap with each other over a range of temperatures and are moved into nonoverlapping relation at temperatures above said range sensed by said temperature sensing means.

8. ln fuel injection apparatus for an internal combustion engine comprising means defining an air inlet duct, adjustable throttle means controlling the flow of air therethrough to the engine, fuel inlet means, and fuel outlet means for connection to one or more injectors, pump means for establishing flow of fuel from said inlet means to said outlet means and for establishing injection pressure for delivery of fuel from said injectors, metering means for delivering a measured quantity of fuel to the outlet means in each cycle of operation of the engine, drive means for driving said metering means in timed relation with the engine, and sensing means for sensing parameters selected to provide a proper air to fuel ratio for a range of engine loads and external conditions of operation, the improvement wherein;

a. said sensing means comprises i. a main pressure sensing means for sensing pressure in said air inlet duct and producing a translatory mechanical output,

ii. a temperature sensing means located for sensing air temperature in said air inlet duct and providing a rotational mechanical output in response to temperature changes sensed thereby,

iii. supplementary pressure sensing means for sensing a sudden change of the pressure of air in said inlet duct in response to sudden opening of said throttle valve means,

b. mechanical means for transmitting mechanical output from all of said sensing means respectively to said metering means without energy amplification, said mechanical means including means for controlling the setting of said metering means in accordance with a combination of the respective parameters sensed by said main and supplementary sensing means and said temperature sensing means, which combination is representative of the air density in said air inlet duct.

9. In fuel injection apparatus for an internal combustion engine comprising means defining an air inlet duct, adjustable throttle means controlling the flow of air therethrough to the engine, fuel inlet means, and fuel outlet means for connection to one or more injectors, pump means for establishing flow of fuel from said inlet means to said outlet means and for establishing injec tion pressure for delivery of fuel from said injectors, metering means for delivering a measured quantity of fuel to the outlet means in each cycle of operation of the engine, drive means for driving said metering 16 means in timed relation with the engine; the improvement comprising the provision in combination of:

a. sensing means for controlling operation ofa metering means and including i. a single pressure sensing means for sensing absolute pressure of air in said air inlet duct,

ii. a temperature responsive sensing means for sensing air temperature in said air inlet duct, each of said pressure and temperature sensing means providing a mechanical output,

b. mechanism for receiving said mechanical output from said pressure sensing means and said temperature sensing means on the one hand and transmitting a mechanical output to said metering means on the other hand without energy amplification for imparting to the latter a setting which is a function of air density within said air inlet duct,

0. closure means having boundary walls defining a chamber common to and enclosing said pressure sensing means and said mechanism for isolating said pressure sensing means and said mechanism from external atmospheric pressure,

d. supplementary pressure sensing means for sensing a sudden change of the pressure of air in said inlet duct in response to sudden opening of said throttle valve means, said supplementary pressure sensing means comprising:

i. an accelerator cylinder within said enclosure means, communicating at one end with said air inlet duct,

ii. an accelerator piston movable axially therein,

iii. biasing means urging said piston in a direction towards said one end,

iv. bleed means providing a control of air leakage from one side of the piston to the other, and

v. means for establishing a connection between said accelerator piston and said mechanism.

10. The improvement according to claim 9 wherein:

a. said main pressure sensing means comprises an evacuated bellows contractable in response to absolute pressure in said air inlet duct,

b. one end of said bellows is operatively connected with said piston to be positionally controlled thereby in a direction axially of said accelerator cylinder,

c. the opposite end of said bellows is operatively connected with said metering means to adjust the setting thereof.

11. The improvement according to claim 10, wherein one end of said bellows is operatively connected with said piston to be positionally controlled thereby in opposite directions axially of said accelerator cylinder.

12. In fuel injection apparatus for an internal combustion engine said apparatus comprising means defining an air inlet duct, an adjustable throttle valve means controlling flow of air therethrough to the engine, fuel inlet means and fuel outlet means for connection to one or more injectors, pump means for establishing flow of fuel from said inlet means to said outlet means at an injecting pressure for delivery from said injectors, metering means for delivering a measured quantity of fuel to said outlet means in each cycle of operation of the engine, and drive means for driving said metering means in timed relation with said engine, the improvement comprising the provision in combination of:

a. sensing means for controlling operation of the metering means and including i. a single pressure sensing means for sensing absolute pressure of air in said air inlet duct, said pressure sensing means being composed of an evacuated enclosure, internal spring means disposed within said enclosure to act in a direction to expand said enclosure, and external spring means located outside of said enclosure and disposed between said enclosure and a fixed surface to act in a direction to oppose such expansion,

ii. a temperature responsive sensing means for sensing air temperature in said air inlet duct, each of said pressure and temperature sensing means providing a mechanical output,

b. mechanism for receiving said mechanical outputs from said pressure sensing means and said temperature sensing means on the one hand and transmitting a mechanical output to said metering means on the other hand for imparting to the latter a setting which is a function of both absolute pressure and air temperature, representative of air density, in said air inlet duct,

c. enclosure means having boundary walls defining a chamber common to and enclosing said pressure sensing means and said mechanism for isolating said pressure sensing means and said mechanism from external and atmospheric pressure,

d. means connecting said pressure sensing means and said mechanism within said chamber for transmitting said mechanical output from said pressure sensing means to said mechanism without traversing any of said boundary walls of said chamber.

13. In fuel injection apparatus for an internal combustion engine said apparatus comprising means defining an air inlet duct, an adjustable throttle valve means controlling flow of air therethrough to the engine, fuel inlet means and fuel outlet means for connection to one or more injectors, pump means for establishing flow of fuel from said inlet means to said outlet means at an injecting pressure for delivery from said injectors, me-

18 tering means for delivering a measured quantity of fuel to said outlet means in each cycle of operation of the engine, and drive means for driving said metering means in timed relation with said engine, the improve ment comprising the provision in combination of:

a. sensing means for controlling operation of the metering means and including i. a single pressure sensing means for sensing absolute pressure of air in said air inlet duct,

ii. a temperature responsive sensing means for sensing air temperature in said air inlet duct, each of said pressure and temperature sensing means providing a mechanical output,

b. mechanism for receiving said mechanical outputs from said pressure sensing means and said temperature sensing means on the one hand and transmitting a mechanical output to said metering means on the other hand for imparting to the latter a setting which is a function of both absolute pressure and air temperature, representative of air density, in said air inlet duct,

c. enclosure means having boundary walls defining a chamber common to and enclosing said pressure sensing means and said mechanism for isolating said pressure sensing means and said mechanism from external and atmospheric pressure,

d. means connecting said pressure sensing means and said mechanism within said chamber for transmitting said mechanical output from said pressure sensing means to said mechanism without traversing any of said boundary walls of said chamber, and

e. valve means responsive to a parameter indicative of low engine temperature and disposed for admitting a controlled quantity of air to said air inlet duct otherwise than by way of said throttle valve means when the engine temperature is below a selected value.

UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION PATENT NO. 3,927 ,653

DATED 1 December 23rd, 1975 INVENTOR( 1 Brian Colin Pagdin It is certified that error appears in the ab0veidentified patent and that said Letters Patent are hereby corrected as shown below:

In the heading of the patent, under [30] Foreign Application Priority Data, change "Mar. 4" to Mar. 3.

Column 1, line 37, change "respecively" to respectively-. Column 2 line 65, change "massflow" to massflow.

Column 3, line 5, change "provides" to is to provide-; line 24, change "sealing" to sensing; line 33, change "a a setting to a setting; line 48 change "anad" to and.

Column 4, line 5, change "of" to a-.

Column 5, line 36, change "supplies" to -supplied.

Column 6 line 9, delete "must"; line 12 delete "which"; line 48, change "to" to the; line 53, change "asembly" to assembly-.

Column 8, line 41, change "virtue" to --a--; line 43, change "This" to ratio-; line 64, change "outout" to output-.

Column 9, line 44, change "in" to from-.

Column 10, line 6, change "produced" to producing; lines lll2, change "impermable" to -impermeable--; line 19, change "virtur" to -virtue-.

Column 11, line 5, change "into" to -onto-; line 55, change "cur-off" to cutoff-; line 61, change "whicch" to -which. Column 12, line 56, change "injector" to --injectors-.

Column 13, line 20, change "connectiing" to --connecting;

line 56, change "injection" to -injecting-.

Column 14 line 13 delete first "and"; line 41, change "meand" to means-.

Column 17, line 26, delete "and".

Signed and ,Sealcd this twenty-fifth Day Of May 1976 [sent ANESI.

RUTH C. MASON C. MARSHALL DANN Arresting Officer (ummixsimwr of Parems and Trademarks 

1. In fuel injection apparatus for an internal combustion engine said apparatus comprising means defining an air inlet duct, an adjustable throttle valve means controlling flow of air therethrough to the engine, fuel inlet means and fuel outlet means for connection to one or more injectors, pump means for establishing flow of fuel from said inlet means to said outlet means at an injecting pressure for delivery from said injector, metering means for delivering a measured quantity of fuel to said outlet means in each cycle of operation of the engine, and drive means for driving said metering means in timed relation with said engine, the improvement comprising the provision in combination of: a. sensing means for controlling operation of the metering means and including i. a single pressure sensing means for sensing absolute pressure of air in said air inlet duct, ii. a temperature responsive sensing means for sensing air temperature in said air inlet duct, each of said pressure and temperature sensing means providing a mechanical output, b. mechanism for receiving said mechanical outputs from said pressure sensing means and said temperature sensing means on the one hand and transmitting a mechanical output to said metering means on the other hand for imparting to the latter a setting which is a function of both absolute pressure and air temperature, representing air density, in said air inlet duct, c. enclosure means having boundary walls defining a chamber in direct communication with the air flow path through said inlet duct, said chamber being cOmmon to and enclosing said pressure sensing means and said mechanism, for isolating said pressure sensing means and said mechanism from the influence of any pressure medium other than the air in said inlet duct, said apparatus being free of any mechanical inputs to said mechanism which traverse said boundary walls, d. means directly mechanically connectiing said pressure sensing means and said mechanism within said chamber for transmitting said mechanical output from said pressure sensing means to said mechanism without traversing any of said boundary walls of said chamber.
 2. The improvement according to claim 1 wherein said pressure sensing means comprises; a. an evacuated bellows, b. means separate from said bellows for providing a reference force against which said bellows operates.
 3. The improvement according to claim 1 wherien a. said pressure sensing means and temperature sensing means include respective means for converting pressure and temperature changes into mechanical energy providing movement of respective output elements, b. said metering means includes an input element movable to vary the quantity of fuel delivered to said outlet means in each cycle of operation of the engine, c. said mechanism is connected to transmit the mechanical energy rquired by such metering means to said input element from said output elements with said pressure sensing means and temperature sensing means themselves forming the energy sources for adjusting the setting of said metering means.
 4. In fuel injection apparatus for an internal combustion engine said apparatus comprising means defining an air inlet duct, an adjustable throttle valve means controlling flow of air therethrough to the engine, fuel inlet means and fuel outlet means for connection to one or more injectors, pump means for establishing flow of fuel from said inlet means to said outlet means at an injection pressure for delivery from said injectors, metering means for delivering a measured quantity of fuel to said outlet means in each cycle of operation of the engine, and drive means for driving said metering means in timed relation with said engine, the improvement comprising the provision in combination of: a. sensing means for controlling operation of the metering means and including i. a single pressure sensing means for sensing absolute pressure of air in said air inlet duct, ii. a temperature responsive sensing means for sensing air temperature in said air inlet duct, each of said pressure and temperature sensing means providing a mechanical output, b. mechanism for receiving said mechanical outputs from said pressure sensing means and said temperature sensing means on the one hand and transmitting a mechanical output to said metering means on the other hand for imparting to the latter a setting which is a function of both absolute pressure and air temperature, representative of air density, in said air inlet duct, c. enclosure means having boundary walls defining a chamber common to and enclosing said pressure sensing means and said mechanism for isolating said pressure sensing means and said mechanism from external and atmospheric pressure, and d. means connecting said pressure sensing means and said mechanism within said chamber for transmitting said mechanical output from said pressure sensing means to said mechanism without traversing any of said boundary walls of said chamber, e. said mechanism including an output member mounted for displacement relatively to said enclosure means along an axis in response to operation of said pressure sensing means and mounted for rotation about said axis in response to operation of said temperature sensing means, and f. said output member having one of its ends operatively connected to or engaged by said pressure sensing means, and the other of its ends enclosed by said enclosure means to avoid presentation of an end face of said output member to atmospheric pressure externalLy of said enclosure means.
 5. The improvement according to claim 4 wherein said output member comprises a cam having a circumferential face presenting a variable throw in the direction of the circumference and presenting a variable radius at different positions along said axis.
 6. In fuel injection apparatus for an internal combustion engine comprising a body having an air inlet duct, an adjustable throttle valve means controlling flow of air therethrough to the engine, fuel inlet means and fuel outlet meand for connection to one or more injectors, pump means for establishing flow of fuel from said inlet means to said outlet means at an injecting pressure for delivery from said injectors, metering means for delivering a measured quantity of fuel to said outlet means in each cycle of operation of the engine, and drive means for driving said metering means in timed relation with said engine, the improvement comprising the provision in combination of: a. valve means responsive to an engine temperature parameter and arranged for admitting a controlled quantity of air to said air inlet duct otherwise than by way of said throttle valve means, b. sensing means for controlling operation of the metering means and including i. a single pressure sensing means substantially isolated in the body of the apparatus from external atmospheric pressure, for sensing absolute pressure of air in said air inlet duct, ii. a temperature responsive sensing means for sensing air temperature in said air inlet duct, each of said pressure and temperature sensing means providing a mechanical output, and c. mechanism operatively connected between said pressure sensing means and said temperature sensing means on the one hand and said metering means on the other hand for imparting to the latter a setting which is a function of both absolute pressure and air temperature in said air inlet duct, said mechanism including an output member mounted for displacement along an axis by operation of said pressure sensing means and for rotation about such axis by operation of said temperature sensing means, and said valve means being operatively associated with said output member for movement between an open position and a closed position in response to rise of temperature sensed by said temperature sensing means.
 7. The improvement according to claim 6 wherein: a. said output member is rotationally supported on a hollow spindle, b. said hollow spindle has a bore which communicates with the external atmosphere, c. said spindle and said output member have ports which register or overlap with each other over a range of temperatures and are moved into non-overlapping relation at temperatures above said range sensed by said temperature sensing means.
 8. In fuel injection apparatus for an internal combustion engine comprising means defining an air inlet duct, adjustable throttle means controlling the flow of air therethrough to the engine, fuel inlet means, and fuel outlet means for connection to one or more injectors, pump means for establishing flow of fuel from said inlet means to said outlet means and for establishing injection pressure for delivery of fuel from said injectors, metering means for delivering a measured quantity of fuel to the outlet means in each cycle of operation of the engine, drive means for driving said metering means in timed relation with the engine, and sensing means for sensing parameters selected to provide a proper air to fuel ratio for a range of engine loads and external conditions of operation, the improvement wherein: a. said sensing means comprises i. a main pressure sensing means for sensing pressure in said air inlet duct and producing a translatory mechanical output, ii. a temperature sensing means located for sensing air temperature in said air inlet duct and providing a rotational mechanical output in response to temperature changes sensed thereby, iii. supplementary pressure sensing means for sensing a sudden change of the pressure of air in said inlet duct in response to sudden opening of said throttle valve means, b. mechanical means for transmitting mechanical output from all of said sensing means respectively to said metering means without energy amplification, said mechanical means including means for controlling the setting of said metering means in accordance with a combination of the respective parameters sensed by said main and supplementary sensing means and said temperature sensing means, which combination is representative of the air density in said air inlet duct.
 9. In fuel injection apparatus for an internal combustion engine comprising means defining an air inlet duct, adjustable throttle means controlling the flow of air therethrough to the engine, fuel inlet means, and fuel outlet means for connection to one or more injectors, pump means for establishing flow of fuel from said inlet means to said outlet means and for establishing injection pressure for delivery of fuel from said injectors, metering means for delivering a measured quantity of fuel to the outlet means in each cycle of operation of the engine, drive means for driving said metering means in timed relation with the engine; the improvement comprising the provision in combination of: a. sensing means for controlling operation of a metering means and including i. a single pressure sensing means for sensing absolute pressure of air in said air inlet duct, ii. a temperature responsive sensing means for sensing air temperature in said air inlet duct, each of said pressure and temperature sensing means providing a mechanical output, b. mechanism for receiving said mechanical output from said pressure sensing means and said temperature sensing means on the one hand and transmitting a mechanical output to said metering means on the other hand without energy amplification for imparting to the latter a setting which is a function of air density within said air inlet duct, c. closure means having boundary walls defining a chamber common to and enclosing said pressure sensing means and said mechanism for isolating said pressure sensing means and said mechanism from external atmospheric pressure, d. supplementary pressure sensing means for sensing a sudden change of the pressure of air in said inlet duct in response to sudden opening of said throttle valve means, said supplementary pressure sensing means comprising: i. an accelerator cylinder within said enclosure means, communicating at one end with said air inlet duct, ii. an accelerator piston movable axially therein, iii. biasing means urging said piston in a direction towards said one end, iv. bleed means providing a control of air leakage from one side of the piston to the other, and v. means for establishing a connection between said accelerator piston and said mechanism.
 10. The improvement according to claim 9 wherein: a. said main pressure sensing means comprises an evacuated bellows contractable in response to absolute pressure in said air inlet duct, b. one end of said bellows is operatively connected with said piston to be positionally controlled thereby in a direction axially of said accelerator cylinder, c. the opposite end of said bellows is operatively connected with said metering means to adjust the setting thereof.
 11. The improvement according to claim 10, wherein one end of said bellows is operatively connected with said piston to be positionally controlled thereby in opposite directions axially of said accelerator cylinder.
 12. In fuel injection apparatus for an internal combustion engine said apparatus comprising means defining an air inlet duct, an adjustable throttle valve means controlling flow of air therethrough to the engine, fuel inlet means and fuel outlet means for connection to one or more injectors, pump means for establishing flow of fuel from said inlet means to said outlet means at an injecting pressure for delivery fRom said injectors, metering means for delivering a measured quantity of fuel to said outlet means in each cycle of operation of the engine, and drive means for driving said metering means in timed relation with said engine, the improvement comprising the provision in combination of: a. sensing means for controlling operation of the metering means and including i. a single pressure sensing means for sensing absolute pressure of air in said air inlet duct, said pressure sensing means being composed of an evacuated enclosure, internal spring means disposed within said enclosure to act in a direction to expand said enclosure, and external spring means located outside of said enclosure and disposed between said enclosure and a fixed surface to act in a direction to oppose such expansion, ii. a temperature responsive sensing means for sensing air temperature in said air inlet duct, each of said pressure and temperature sensing means providing a mechanical output, b. mechanism for receiving said mechanical outputs from said pressure sensing means and said temperature sensing means on the one hand and transmitting a mechanical output to said metering means on the other hand for imparting to the latter a setting which is a function of both absolute pressure and air temperature, representative of air density, in said air inlet duct, c. enclosure means having boundary walls defining a chamber common to and enclosing said pressure sensing means and said mechanism for isolating said pressure sensing means and said mechanism from external and atmospheric pressure, d. means connecting said pressure sensing means and said mechanism within said chamber for transmitting said mechanical output from said pressure sensing means to said mechanism without traversing any of said boundary walls of said chamber.
 13. In fuel injection apparatus for an internal combustion engine said apparatus comprising means defining an air inlet duct, an adjustable throttle valve means controlling flow of air therethrough to the engine, fuel inlet means and fuel outlet means for connection to one or more injectors, pump means for establishing flow of fuel from said inlet means to said outlet means at an injecting pressure for delivery from said injectors, metering means for delivering a measured quantity of fuel to said outlet means in each cycle of operation of the engine, and drive means for driving said metering means in timed relation with said engine, the improvement comprising the provision in combination of: a. sensing means for controlling operation of the metering means and including i. a single pressure sensing means for sensing absolute pressure of air in said air inlet duct, ii. a temperature responsive sensing means for sensing air temperature in said air inlet duct, each of said pressure and temperature sensing means providing a mechanical output, b. mechanism for receiving said mechanical outputs from said pressure sensing means and said temperature sensing means on the one hand and transmitting a mechanical output to said metering means on the other hand for imparting to the latter a setting which is a function of both absolute pressure and air temperature, representative of air density, in said air inlet duct, c. enclosure means having boundary walls defining a chamber common to and enclosing said pressure sensing means and said mechanism for isolating said pressure sensing means and said mechanism from external and atmospheric pressure, d. means connecting said pressure sensing means and said mechanism within said chamber for transmitting said mechanical output from said pressure sensing means to said mechanism without traversing any of said boundary walls of said chamber, and e. valve means responsive to a parameter indicative of low engine temperature and disposed for admitting a controlled quantity of air to said air inlet duct otherwise than by way of said throttle valve means when the engine teMperature is below a selected value. 